1. Field of the Invention
This invention relates to an image-printing method and device for printing an image formed by arranging at least one image element.
2. Prior Art
Generally, to print an image (whole image) containing, as image elements thereof, images of characters, such as letters, numerals, symbols, simple figures, etc., or images of character strings each formed by arranging such characters, it is required to read out font data corresponding to text data (character code) of each of the characters from a ROM or the like storing predetermined font data, and then, based on the font data read out, convert the text data to image data and arrange the image data in a predetermined area of a memory, thereby forming whole image data representative of the whole image.
As fonts (font data) for converting character codes to image data corresponding thereto, there have been conventionally employed a dot font (bitmap font) in which each character image is represented by a set of pixels (dots) in a manner defined by a dot matrix of a predetermined size, and an outline font in which each character image is defined by the coordinates of several reference points for forming contour lines of the image, the attributes of lines (straight lines or curves) connecting the reference points to each other, etc.
The dot font provides images of characters fixed in size, and hence to print characters (character images) having various sizes in a clear and attractive manner, it is required to store font data suitable for each of the sizes for use, which necessitates a very large memory capacity. To form an image (enlarged image) by arranging enlarged image elements of character images or the like, especially to enlarge character images or the like, by using only dot font data of a predetermined size, it is required to replace each image pixel of each original character image by a plurality of image pixels. On the other hand, to form a reduced image, image pixels have to be thinned.
In these cases, curved portions of the resulting character images are jagged, and to remove jaggedness from them, it is required to carry out a replacement process, in which blank pixels and image pixels at the curved portions are replaced by each other in a manner adjusted to the original curve such that the curved portion is smoothed. That is, so-called smoothing processing has to be carried out. However, even through the smoothing processing, it is difficult to form a neater image than an image formed based on the outline font discussed hereafter.
The outline font provides character images each defined by the coordinates and attributes of contour lines thereof. Hence, the dot matrix of a character image having a desired size can be determined simply by converting the character code to image data corresponding thereto according to the desired size. That is, the font data as reference is expanded or reduced in size by calculation during the conversion of the character code, so that a clear enlarged or reduced image can be formed by converting the character code of the original character image according to the desired size and arranging the resulting character image in a predetermined memory area.
Therefore, when a whole image comprised of image elements, such as character images is enlarged or reduced to use the same as a basic image for printing, that is, when it is required to enlarge or reduce and arrange image elements, such as character images, outline fonts are generally used. Further, printing apparatuses necessitating the above processing are generally provided with a ROM or the like for storing outline fonts.
However, some images as the aforementioned whole image cannot be formed based on the outline font. For instance, if a whole image includes, as image elements thereof, not only character images and the like which can be converted from character codes based on the outline font but also registered nonstandard character images or registered images, the latter images cannot be formed based on the outline font since each of these images is normally registered in the form of a dot matrix. Therefore, even when the enlarged image of the whole image is desired to be obtained, it is impossible to form the enlarged image by directly enlarging and arranging all the image elements through conversion based on the outline font.
As described above, when a whole image of a normal (reference) size i.e. data representative of the image cannot be formed based on the outline font, to obtain a desired image (basic image), e.g. an enlarged image, which corresponds to the whole image, it is required to create the desired image based on dot matrices (including a dot font). More specifically, when a desired image(basic image) is to be formed by enlargement or reduction of image elements, it is required to arrange each image element enlarged or reduced in the form of a dot matrix in a memory area and thereafter smooth it, or alternatively to enlarge or reduce each image element and smooth the same before arrangement in the memory area. However, in these cases, even if each image element is smoothed as described above, it is difficult to obtain as clear an image as formed based on the outline font.